THE sound of the voice that emerged from the crackle of the cassette tape underlined the chilling reality a West Midlands family had become embroiled in.

Sounding near to tears, kidnapped teenage Shropshire heiress Lesley Whittle could be heard trying to reassure her desperate mother. Forced to record the one minute and 29 second message by her cold-hearted kidnapper, the A-level student said: “There is nothing to worry about mum. I am okay.”

Lesley, 17, was found to be missing from her bedroom of the family home in Beech Croft, Highley, Bridgnorth, Shropshire, about 7am on January 14, 1975.

A ransom note, demanding £50,000 for her safe return, was found punched out on Dymo plastic tape, normally used for marking binders and folders. It was so detailed it stretched a foot-and-a-half in length.

However, it wasn’t until a month later that police revealed Lesley’s kidnapper was the killer dubbed the Black Panther.

The Black Panther got his nickname from the way he dressed all in black, hid his features behind a balaclava and sneaked stealthily around in the dead of night to commit his crimes.

He had eluded police for years as he burgled homes and robbed post offices. In each case, the post offices were broken into by a robber who would wake his victims and demand they hand over the safe keys.

But his savage wave of crime took a dramatic – and deadly – turn on February 15, 1974, when the hooded robber shot dead 54-year-old Donald Skepper at his post office in Harrogate, Yorkshire.

Seven months later he struck again, killing Derek Astin, 43, during a struggle at his sub-post office in Accrington, Lancashire.

Two months later, the ‘Panther’ emerged from the shadows to strike in the Black Country.

On a chilly November day, Sidney Grayland and his wife Dorothy were in their post office, in Langley, Warley, when he struck.

Mr Grayland, 54, had gone to lock up the rear of the store when his wife heard a loud bang as he was blasted in the stomach.

She was beaten around the head and left for dead.

Police believe the Panther did not wear his traditional balaclava because he didn’t intend for either victim to live. He escaped with just £1,000.

And then the Black Panther went quiet – until January 1975 when he kidnapped Miss Whittle.

Police investigating the seemingly unconnected shooting of security guard Gerald Smith also that January found the bullets matched those in the Post Office murders. It was thought Mr Smith was shot after disturbing the Panther as he set up his ransom trail.

In March 1975, almost two months after the kidnapping, police descended into the labyrinth of dark tunnels beneath Staffordshire’s Bathpool Park, near Kidsgrove, in the search for Miss Whittle.

Her body was found hanging by a wire from the bottom ledge of a 30ft sewer shaft. Her feet were inches from the ground after the wire had snagged around a stanchion and she had died of a fatal shock to the nervous system.

However, the Panther had made the tiniest of mistakes that was to unmask him.

A partial fingerprint on a notepad found in the drainage complex led to officers identifying him as Donald Neilson.

His capture, when it came, could hardly have been more mundane.

In December 1975, two bobbies were on patrol in Mansfield, Nottinghamshire, when they spotted a man near a sub-post office.

But as they approached the man he pulled out a shotgun and ordered the pair to get back in the vehicle in a desperate bid to flee.

But his escape bid ended minutes later when one of the constables lunged at Neilson, causing the gun to go off. Two passers-by raced to help and the Panther was handcuffed to railings.

For several days Neilson, then 39, refused to answer questions. But he finally made a full confession, saying he had accidentally knocked Lesley off the ledge.

On the opening day of the trial, June 14, 1976, Neilson pleaded guilty to kidnap and demanding money with menaces but not guilty to murder.

The prosecution accused the builder of pushing Miss Whittle to her death from a precarious ledge amid fears he was about to get snared by police as his ransom plans went awry. But Neilson said she slipped.

Taking the stand, his violent temper soon emerged.

In a shrill voice he declared: “I disclaim all responsibility for her death. I did not kill her. My conscience is clear as far as the act of killing her. I did not.”

The jury disagreed and on July 1 they returned a unanimous guilty verdict.

Days later, he was convicted of the murders of Mr Skepper, Mr Astin and 54-year-old Sidney Grayland.

Britain’s most wanted criminal was jailed for life on all four murder charges, including that of Lesley Whittle.

* The coroner's inquest into the death of Neilson will open on Wednesday.

On Saturday, the 75-year-old was taken to Norfolk & Norwich University Hospital from Norwich prison with breathing difficulties and was pronounced dead at about 6.45pm on Sunday, the Prison Service said.

The inquest into his death will open at 10am at the Coroner's Court in Norwich.

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The Black Panther: From burglary, to murder ... to jail

Donald Neilson, left a trail of murder as he stalked the country. Here are the key dates:

Early 1970s police in Lancashire and West Yorkshire link a series of burglaries at post-offices

September 1975, Derek Astin, 43, shot dead during a struggle at his sub post-office in Accrington, Lancashire.

November 1974, Sidney Grayland and his wife Dorothy, known to friends as Peggy, targeted in their post office, in Langley, Warley. Mr Grayland, 54, is shot dead, Peggy is beaten and left for dead.

January 14, 1975, Lesley Whittle, 17, is found missing from her bedroom of the family home in Beech Croft, Highley, Bridgnorth, Shropshire, about 7am. A £50,000 ransom made for her safe return.

January 17, 1975, Lesley’s anguished brother Ronald was dispatched to Bathpool Park, in Kidsgrove, Staffordshire, to make the demand but he can’t find the instructions which had been left behind a telephone kiosk.

On the same night security guard Gerald Smith is shot and injured by Neilson after disturbing the crook as he laid the ransom trail.

February 1975, police link the kidnap of Miss Whittle to the post office murders

March 7 1975, Miss Whittle is found dead is the underground labyrinth of drainage passageways in Bathpool Pool.

December 1975, Donald Neilson is finally arrested by two policemen on patrol in Mansfield, Nottinghamshire, after being seen near a sub-post office.

June 14, 1976, Neilson pleaded guilty to the kidnap of the 17-year-old and demanding money with menaces but not guilty to her murder on the first day of his trial.

July 1 1976, after one hour and 55 minutes of deliberations jury returns a unanimous guilty verdict.

July 1976, Neilson also convicted of the three post office murders and is jailed for life.

In 2008 and suffering from Motor neurone disease, Neilson appealed his sentence, requesting it be muted to a maximum of 30 years. High Court judge Mr Justice Teare ruled the killer must never be released from prison.